K-STATE RESEARCH AND EXTENSION WOOLLYLEAF BURSAGE BIOLOGY AND CONTROL

Woollyleaf bursage, [Ambrosia grayi percent are common (Finney County (A. Nels.) Shinners], also known as bur Noxious Weed Economic Impact). , is a perennial noxious weed native Woollyleaf bursage is more competitive to . It is a member of the Composite with summer crops than with winter wheat family and was referred to previously as because woollyleaf bursage growth is Franceria tomentosa in the false ragweed minimal during much of the winter wheat family. Taxonomists were not able to life cycle. However, in dry years, distinguish between Ambrosia grayi and woollyleaf bursage will deplete soil mois- Franceria tomentosa and thus the accepted ture for fall planted wheat and thereby current Latin name is Ambrosia grayi. reduce grain yield significantly. Woollyleaf bursage infests more than 80,000 acres in Kansas, primarily in the western half of the state. It is adapted to low areas where water runoff col- lects in cultivated fields or in non- cropland areas. The collection of water and the deep perennial root system, which can reach a depth of 15 feet, allow woollyleaf bursage to survive Woollyleaf bursage is one of the extended periods of drought or harsh weeds classified as noxious within weather. These circumstances make it very Kansas according to the Kansas Noxious difficult to control. The development of Weed Law. This law requires that all irrigation may be extending the areas of noxious weeds be controlled. A copy adaptation beyond the immediate ponding of the Noxious weed law can be obtained areas, raising concerns that woollyleaf from the Health Division, Kansas bursage acreage is expanding. Department of Agriculture, 901 S. Kansas, Woollyleaf bursage is extremely Topeka, KS 66612. competitive with crops, and can reduce grain yield by 100 percent in dry years. Even with irrigation, losses of 40 to 75 WOOLLYLEAF BURSAGE BIOLOGY AND CONTROL 2

Biology and Growth Habit During late July or early August, woollyleaf bursage flower development begins. A single flower- ing stalk may protrude from each stem. Inconspicu- ous, greenish-gray male flowers are borne on the tip and upper portion of the flowering branch. One to several greenish-gray female flowers are borne in the upper leaf axils, further down the stem than the male flowers. Where several female flowers develop in a leaf axil, clusters of burs develop. The fruits (burs), which arise from the female 1 flowers, can be up to /3 inch in length, are light-tan, and the hull is covered with sharp, hooked barbs. Inside the bur are two compartments that each poten- tially contain a seed. At Lubbock, , a population Woollyleaf bursage is a deep rooted perennial. Root excavation showed that in a 4-year-old woollyleaf bursage stand had many roots penetrating 1 the soil to a depth of 6 feet or more and measuring /8 1 to /4 inch in diameter. Several lateral roots branched from the tap root. The lateral roots were smaller in diameter and seldom developed below a soil depth of 10 inches. The average depth of lateral root develop- ment was 3 to 4 inches. Lateral roots were found as shallow as 0.25 inches. New plants arise from the vegetative buds, which develop on the root stocks, thus contributing to the spread of woollyleaf bursage. Tillage also can redistribute vegetative buds, aiding the spread of density of seven to 12 stems per square foot produced woollyleaf bursage. 380 to 460 burs per square foot. Shoots of In germination tests, seeds that remained encap- woollyleaf bursage sulated within the bur did not germinate regardless of will grow from root exposure to a range of constant or alternating tem- buds, emerging peratures. Germination occurred only after the fruits during April. It has were split and the seeds exposed to constant tempera- silvery-grayish tures of 12°, 50°, 70°, or 80°F for 21 days and then foliage covered with exposed to fluctuating temperatures ranging from 12 dense white hairs, to 85°F for 149 days. Sixteen percent germination which gives the occurred when unsplit burs were exposed to concen- showy silvery-gray trated sulfuric acid for 60 minutes and constant 70°F appearance. It has temperature for 21 days. Seed contributes to the erect growth, 12 to spread of woollyleaf bursage and likely is a source of 24 inches tall, and new infestations. pinnately divided leaves with three to seven lobes. WOOLLYLEAF BURSAGE BIOLOGY AND CONTROL 3

Woollyleaf Bursage Control control ratings 11 months after treatment were lower, Controlling woollyleaf bursage requires persis- indicating that some woollyleaf bursage had survived tence and an integrated approach. Woollyleaf bursage the herbicide treatment. The lower ratings 11 months spreads by roots and seed. Thus, it is important to minimize or prevent seed production. This can be acccomplished by using chemicals and tillage. Single tillage operations provide little long-term control of woollyleaf bursage. reported that control- ling woollyleaf bursage with tillage would require tillage 3 to 4 inches deep every 14 to 21 days for 2 to 3 years. Current residue requirements for cropland would not allow this excessive tillage needed to control woollyleaf bursage. When tilling the woollyleaf bursage infested areas, it is important to clean woollyleaf bursage roots from tillage equip- ment before tilling uninfested areas of the field or other fields to prevent its spread. Effective after treatment compared to 9 months after treat- chemical control of ment held true for nearly all treatments. This woollyleaf bursage stresses the importance of monitoring treated areas requires systemic for regrowth for several months and perhaps 1 and 2 herbicides that will years after application to ensure that woollyleaf move with the bursage is controlled. carbohydrate Other herbicides provided some control of reserves deep into woollyleaf bursage, however, control was not consis- the woollyleaf tent over timings and years. It is unlikely that a single bursage root system. herbicide treatment will eliminate woollyleaf bursage. Herbicide treatment One to several retreatments in subsequent years will be during the time required for complete woollyleaf bursage control. when significant carbohydrate is being transported into the root system will provide the most effective control. However, treatments must be applied before a fall killing frost to allow herbicide uptake and translocation. Research at the Southwest Research-Extension Center in Garden City, Kansas suggests that herbicide applications should be made to woollyleaf bursage during the flowering stage (Table 1). Flowering will begin in late July or early August. August applied treatments generally gave better control than treatments applied in September. Tordon Control of woollyleaf bursage with August or tank mixed with Banvel or 2,4-D ester controlled September treatments can depend on available mois- woollyleaf bursage at both timings in both years ture and growing conditions. Stress from drought when evaluated 9 months after treatment. However, during these time periods is common with woollyleaf WOOLLYLEAF BURSAGE BIOLOGY AND CONTROL 4

Table 1. Woollyleaf bursage control 9 and 11 months after treatment with postemergence herbicides applied at flowering in mid-August or 30 days later in mid-September at Garden City, Kansas.

Application timing1 1991 1995 AVG 30 30 30 Treatment Rate Flwr DAF Flwr DAF Flwr DAF AVG (lbs/a) (% control 9 months after treatment) Untreated 0 1 1 22 20 12 10 11 Stinger2 0.12 2 14 39 7 21 10 16 Stinger2 0.25 26 70 66 52 46 61 54 Starane2 + Banvel 0.75+0.5 90 19 64 68 77 47 60 Starane2 + 2, 4-D amine 0.25+1 96 14 65 32 80 23 51 Tordon + Banvel 0.25+0.5 98 99 100 100 99 99 99 Tordon + 2, 4-D LVE 0.25+1 100 94 100 100 100 97 99 Roundup + Banvel 1.5+1 45 44 74 52 59 48 53 Roundup + 2, 4-D LVE 1.5 96 9 68 30 82 20 51 LSD3=0.05 29 33 19 14

(lbs/a) (% control 11 months after treatment) Untreated 0 0 0 14 7 7 3 5 Stinger2 0.12 7 4 16 26 12 15 13 Stinger2 0.25 25 46 21 33 23 39 31 Starane2 + Banvel 0.75+0.5 65 5 20 33 42 19 31 Starane2 + 2, 4-D amine 0.25+1 85 11 41 3 63 7 35 Tordon + Banvel 0.25+0.5 77 85 69 99 73 82 77 Tordon + 2, 4-D LVE 0.25+1 98 79 89 69 93 74 84 Roundup + Banvel 1.5+1 34 24 28 9 31 16 24 Roundup + 2, 4-D LVE 1.5 75 24 13 30 44 27 36 LSD3=0.05 31 32 19 14

1 Flwr = Flowering, mid-August; 30 DAF = Thirty days after first treatment, mid-September. 2 Starane or Stinger were not registered for woollyleaf bursage control as of March 1997. 3 LSD = Any two values differing by more than the LSD value found at the base of the columns are significantly different from one another. WOOLLYLEAF BURSAGE BIOLOGY AND CONTROL 5

Table 2. Herbicides for control of woollyleaf bursage. Cropland

Herbicide and pounds Formulated active ingredient/acre product/acre Comments

Banvel 1 to 2 qt Broadcast or spot treat to actively 1 to 2 growing plants after crop harvest and before a killing frost. Treatment during or after flowering will increase control.

Banvel + 2,4-D 1 pt + 1 qt Apply to regrowth in late summer or fall. 0.5 + 1 For each pint of Banvel applied, delay wheat planting for 45 days after application.

Roundup Ultra + Banvel 1 to 2 qt + 1 pt Apply with 2% v/v ammonium sulfate. 0.38 to 0.75 + 0.5 Apply when plants are at or beyond the flowering stage and actively growing.

2,4-D LVE 2 qt Apply during fallow period during 2 active growth at the bud stage.

Tordon + 2,4-D 1 pt + 1 qt Used in fallow when woollyleaf 0.25 + 1 bursage is flowering, or in the fall. Allow 60 days following treatment before planting wheat. Do not plant susceptible broadleaf crops for at least 36 months.

Pasture, Rangeland, and noncropland Any of the above treatments, with the exception that Roundup should not be used on pasture or rangeland.

Banvel 2 to 6 qt For suppression and top-growth 2 to 6 control. Can injure grasses.

Arsenal 2 to 6 pt For use on noncropland areas only. Will 0.5 to 1.5 control several other broadleaf and grass species. The addition of a nonionic surfactant at 0.5% v/v is recommended. WOOLLYLEAF BURSAGE BIOLOGY AND CONTROL 6 bursage. Herbicide effectiveness likely will be re- Literature Cited duced when plants are severely stressed. In a study Anonymous. 1995. Finney County Noxious Weed conducted in Seward County, Kansas during 1995, Economic Impact. In Noxious Weed Update Novem- heavy rains fell after the drought stressed plants were ber 1995. Plant Protection & Weed Control Section, treated in August. The study remained under water Kansas Department of Agriculture, Topeka, KS. for at least 2 weeks. Nine months after treatment, no Anonymous. 1986. Noxious Weed Distribution herbicide treatments provided any control of Summary 1986. Plant Protection & Weed Control woollyleaf bursage. Drought and flooding can have Section, Kansas Department of Agriculture, Topeka, an adverse affect on woollyleaf bursage control and KS. can be a common occurrence in Kansas during Cooley, A.W. and D.T. Smith. 1971. Seed August and September. germination of Woollyleaf bursage, Texas blueweed Herbicides registered for woollyleaf bursage and groundcherry. Texas Agr. Exp. Sta. Progress control are Banvel, 2,4-D, Roundup, Tordon, and Report 3197. Texas A&M, College Station, TX. Arsenal (Table 2). Various combinations of these Currie, R. 1996. Effects of Time of Application herbicides may be more effective than any one single of Eight Herbicide Combinations for Woollyleaf herbicide applied alone. Read and follow label Bursage (bur ragweed) control. In Southwest Re- directions for herbicide use rates and plant back or search-Extension Center Field Day 1996 Report of grazing restrictions. Progress 768. P. 43-45. Feltner, K.C., J.L. Hatfield, and J.H. Hillis. 1971. Bur Ragweed — An Old Weed with New Life Brand names appearing in this publication are in Western Kansas. Research Paper #4. Agricultural used for product identification. No endorse- Experiment Station. Kansas State University, Man- ment is intended, nor is criticism of similar hattan, KS. products not mentioned. Persons using such Jeffery, L.S. and L.R. Robinson. Know and products assume responsibility for their use in control Woollyleaf Bursage and Skeletonleaf accordance with current label directions of the Bursage. E.C. 69185. Cooperative Ext. Service, manufacturer. University of Nebraska, Lincoln, NE. Peterson, D.E., D.L. Regehr, P.D. Ohlenbusch, W.H. Fick, P.W.Stahlman, and D.K. Kuhlman. 1996. Authors: Chemical Weed Control for Field Crops, Pastures, Curtis R. Thompson Rangeland, and Noncropland. SRP 748. P. 55. Agri- Area Extension Specialist, Crops and Soils cultural Experiment Station, Kansas State University, Southwest Kansas Manhattan, KS. Sand, P.F. and M.K. McCarthy. 1964. Randall S. Currie Woollyleaf Franseria. University of Nebraska, Lin- Research Weed Scientist coln, NE. KSU Southwest Research-Extension Center

Dallas E. Peterson Extension Weed Science Specialist Extension Agronomy

Kansas State University Agricultural Experiment Station and Cooperative Extension Service, Manhattan MF-2239 February 1997 Issued in furtherance of Cooperative Extension Work, acts of May 8 and June 30, 1914, as amended. Kansas State University, County Extension Councils, Extension Districts, and Department of Agriculture Cooperating, Richard D. Wootton, Associate Director. All educational programs and materials available without discrimination on the basis of race, color, national origin, sex, age, or disability. February 1997 File Code: Crops & Soils. 5-4 MS 2-97—5M